4" Stainless Steel Inline Anti-Surge Flaps Assembly (Pair) 

4" Inline Anti-Surge Flap Assembly. For 4" Hose connections. If your tip don't have an integrated flap and you don't have the ability to mount an external flap, these inline flaps will do the trick. Sold in Pairs. Measures 2-3/8" Long x 4" in diameter.